JP2007171408A - Illuminator, liquid crystal display device, illuminator control method, illuminator control program, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain an illuminator which can converge white balance quickly by a simple control from activation irrespective of combination of CCHLs and LEDs for expanding a color reproduction range. <P>SOLUTION: The illuminator relating to this invention determines, when activating the lighting device, (S1c) a driving amount in turning on the LEDs according to a driving amount (S1a) of the CCFL in the previous operation and temperature (S1b) inside the lighting device, and then turns on the CCFL (S2) and the LEDs (S10). Therefore, immediately after starting lighting, white balance of composite light of CCFL and LED can be approximate to a target value, and white balance of the composite light can be converged to the target value earlier. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to control of a light source in an illumination device having a plurality of types of light sources.

  2. Description of the Related Art In a transmissive liquid crystal display device used for a notebook computer, a computer monitor, a television receiver, and the like, conventionally, a cold cathode fluorescent lamp (CCFL: Cold Cathode Fluorescent Lamp) is a lighting device installed on the back of a liquid crystal panel, so-called It has been used as a backlight. However, in recent years, light emission efficiency and the like in a light emitting diode (LED) have been improved, and the cost has been reduced, so that the LED is being used as a backlight of a liquid crystal display device.

  When an LED is used for a backlight, a red (hereinafter also abbreviated as R) light-emitting diode (hereinafter also abbreviated as R-LED), a green (hereinafter also abbreviated as G) light-emitting diode (hereinafter abbreviated as G) in order to produce necessary white light. It is common to use a combination of three types of light emitting diodes: blue (hereinafter also abbreviated as B) and blue (hereinafter also abbreviated as B) light emitting diodes (hereinafter also abbreviated as B-LED). In a backlight using CCFLs and LEDs as light sources, it is important to control the white balance of the synthesized light with good cost performance because it produces synthesized light from a plurality of types of light sources having different characteristics.

  For example, in Patent Document 1, a backlight for illuminating a liquid crystal panel is composed of a plurality of cold cathode fluorescent lamps and an array of a plurality of light emitting diodes arranged adjacent to the cold cathode fluorescent lamps, according to the screen brightness. A liquid crystal display device that is driven by combining a cold cathode fluorescent lamp and a light emitting diode is disclosed. In this liquid crystal display device, the decrease in luminance due to the low temperature of the cold cathode fluorescent lamp is compensated by increasing the luminance of the white or R, G, B light emitting diodes. The current applied to the cathode fluorescent lamp is reduced to prevent the efficiency from being lowered due to the high temperature. And the brightness | luminance which the brightness | luminance of the cold cathode fluorescent lamp fell is compensated by the brightness | luminance improvement of a light emitting diode.

  Patent Document 2 discloses an illumination device that uses three types of red LEDs, green LEDs, and white LEDs as light sources, and the white LEDs use YAG-based white LEDs. A YAG white LED is a phosphor containing a material composed of yttrium aluminum garnet (commonly called YAG) and a compound thereof, that is, a material system including yttrium aluminum garnet and a compound thereof for direct photoelectric conversion light of an LED chip. Refers to a light emitting diode (LED) that can convert the wavelength of the light and, as a result, emit white light.

Further, Patent Document 3 discloses a method for adjusting a display device that can easily perform white balance adjustment even when the emission characteristics of LEDs vary. In this adjustment method, each color LED of red, green, and blue is caused to emit light while being independently PWM controlled within a unit light emission period, and the chromaticity at that time is measured by a luminance / chromaticity meter, and the measurement value is set as a target. The deviation from the white balance value is calculated, the duty ratio for each color LED is corrected according to the deviation, and each color LED is caused to emit light again. The duty ratio of each color LED when the deviation is within a predetermined allowable range is determined as the duty ratio. Store in the storage register.
JP2003-140110 (released on May 14, 2003) JP 2004-253309 (released September 9, 2004) JP-A-2004-309509 (released on November 4, 2004)

  In the liquid crystal display device disclosed in Patent Document 1, CCFLs and LEDs are combined, and R, G, and B color LEDs are used as the LEDs. Although there is no description regarding the control of white balance, there is a description that the brightness of CCFL is controlled. Therefore, for white balance control, R-LED, G-LED, and B-LED are added to CCFL. It is necessary to control the luminance of each type of light source, and there is a problem that the control becomes complicated.

  In addition, the illumination device disclosed in Patent Document 2 has a problem in that cost performance is poor because the unit price per unit luminance is higher than that of a fluorescent lamp and only LEDs with low luminous efficiency are used as a light source. There is.

  Further, in the adjustment method disclosed in Patent Document 3, the light emission luminance of each of the R, G, and B color LEDs is adjusted to bring the white balance to the target white balance value, which makes the adjustment complicated. There are challenges.

  In addition, it is conceivable to perform control for converging white balance using CCFL and R-LED as a target, such as a white point, but in this case, there are the following problems.

  For example, in a light source using CCFLs and R-LEDs, the parameters that can be moved to control white balance are CCFL brightness and / or R-LED brightness. CCFL emits light of B + G or R + G + B, but the amount of light emission of each color cannot be individually controlled. Therefore, when the CCFL is manufactured, the mixing ratio of the R, G, and B phosphors varies. Variations in chromaticity among CCFL individuals will occur.

  Moreover, the light emission efficiency of the phosphor of CCFL decreases due to aging. The rate of decrease tends to be greater in efficiency reduction of the B phosphor than the R and G phosphors. Therefore, the chromaticity of the CCFL light shifts in the yellow direction due to secular change. Further, the change in luminance due to temperature tends to increase in luminance as the CCFL is warmed up after being turned on, but the LED tends to decrease in luminance on the contrary. The decrease in luminance due to secular change tends to decrease at a constant rate in the LED, but the CCFL tends to decrease in luminance first and then decrease.

  When making composite light using CCFL having the above characteristics and R-LED, it is impossible to always converge the white balance to a target point and obtain an achromatic light source. There is a problem that cannot be done.

FIG. 7 shows a state of control for adjusting the white balance of the light source to the target white point by adjusting the luminance of the R-LED using a light source using CCFL and R-LED emitting B and G. FIG. 7 is a plot of the following chromaticity points on the chromaticity coordinates of the XYZ color system. That is, the target for white balance convergence (white point), the chromaticity point of the R-LED, the chromaticity point (a ₀ ) of the initial CCFL, and control for adding the R-LED light to the initial CCFL light once. chromaticity point closer to perform target (a _1), first-time control result feedback and a second time, the initial color point of performing a control to apply the light of R-LED to light CCFL (a _2), CCFL chromaticity point (b ₀ ) after 100,000 hours have elapsed, and the chromaticity point (b ₁ ) that is close to the target by performing control to add the light of the R-LED to the CCFL light after 100,000 hours has elapsed, This is the chromaticity point (b ₂ ) where the control result of the first time is fed back and the second control is performed to add the light of the R-LED to the CCFL light after 100,000 hours have elapsed.

In order to control only the luminance of the R-LED, the chromaticity point of the combined light of the CCFL and the R-LED is changed in the initial CCFL state in accordance with the change in the luminance of the R-LED. a ₀ ) and the chromaticity point of the R-LED on the line connecting the chromaticity point (a ₀ ) to the chromaticity point (a ₁ ) and the chromaticity point ( It moves every time control is applied to a ₂ ), gradually approaches the target, and converges.

However, in the CCFL after 100,000 hours have elapsed, the chromaticity point (b ₀ ) moves to the G side with the above-described deterioration of B. When white balance is controlled by the R-LED, the chromaticity point of the combined light of the CCFL and the R-LED increases from the chromaticity point (b ₀ ) to the chromaticity point (b ₁ ) as the luminance of the R-LED increases. To the chromaticity point (b ₂ ), and moves on a straight line connecting the chromaticity point (b ₀ ) and the chromaticity point of the R-LED. Since the white point that is the target is not on the straight line, if control is performed so that the white balance converges on the target, the target chromaticity point (b ₂ ) closest to the target will not be converged. This results in convergence in the vicinity or hunting.

In the above algorithm for controlling the white balance to the chromaticity point closest to the white point that is the target, no consideration is given to the color, so the chromaticity point closest to the target (b ₂₎ as the CCFL changes over time. ) Comes to the green area, which gives the user a feeling of strangeness.

  The most notable issue is that when the CCFL and LED are always driven at a constant driving amount when the CCFL and LED are turned on, the white balance immediately after the start of driving depends on the temperature and aging. May deviate significantly from the point. When the deviation becomes large, there is a problem that the time required for convergence to the target point becomes long.

  The present invention has been made in view of the above-described problems, and its object is to achieve white balance by simple control from the start-up despite the combination of CCFL and LED for expanding the color reproduction range. Is to realize an illumination device capable of quickly converging.

(1) Control of start drive amount based on drive amount and temperature during previous operation In order to solve the above problems, the lighting device according to the present invention emits different colors of the first light source and the second light source. And determining the driving amount when the second light source is turned on according to the temperature in the lighting device and the driving amount of the first light source during the previous operation, Control means for turning on the second light source is provided.

  The reason why the lighting device according to the present invention includes the first light source and the second light source that emit different colors in the configuration is that the color reproduction range is expanded by combining two types of light sources having different performances. This is to improve the performance due to the above.

  However, as described in the problem in the prior art, when the first light source and the second light source are turned on, when the driving is started with a constant predetermined value as the driving amount of these light sources, the white balance immediately after the start of the driving is performed. However, it may deviate significantly from the target value. If the deviation is large, it is difficult to quickly converge the white balance of the combined light to the target value.

  Therefore, when the first light source and the second light source are turned on, the driving is not started with a fixed value as the driving amount of these light sources, but the temperature in the lighting device and the first time during the previous operation are not started. The driving amount when the second light source is turned on is adjusted according to the driving amount of the light source.

  By adjusting the driving amount at the time of lighting, the white balance of the combined light is made closer to the target value immediately after the start of lighting, and the convergence of the combined light to the target value of white balance is accelerated.

  Note that the timing of turning on the first light source and the second light source may be simultaneous, or the first light source may be turned on first and then the second light source may be turned on. Further, the timing for determining the driving amount when the second light source is turned on may be before the second light source is turned on, and does not depend on the timing when the first light source is turned on.

  According to the above configuration, since the white balance of the composite light can be made closer to the target value immediately after the start of lighting, the convergence of the white balance of the composite light to the target value can be accelerated. There is an effect that can be.

(2) Obtaining the driving amount when the second light source is turned on from a table In order to solve the above problems, the lighting device according to the present invention is configured such that the control means drives the driving amount when the second light source is turned on. Is determined, a table including a temperature in the lighting device, a driving amount of the first light source at the previous operation, and a driving amount at the time of lighting of the second light source is used. .

  In this configuration, the table referred to by the control means is, for example, a two-dimensional table in which the temperature in the lighting device is taken for each row and the driving amount of the first light source during the previous operation is taken for each column. This table is prepared in advance at the design stage. In this table, the driving amount when the second light source is turned on is uniquely determined from a certain temperature and the driving amount of the first light source.

  According to the above configuration, since the table is used when the driving amount when the second light source is turned on, the second light source is compared with the case where the driving amount when the second light source is turned on using a calculation formula. There is an effect that the drive amount when the light source is turned on can be obtained quickly.

(3) The first light source is a cold cathode fluorescent lamp The lighting device according to the present invention is characterized in that the first light source is a cold cathode fluorescent lamp.

  In this configuration, the illumination device according to the present invention uses a cold cathode fluorescent lamp as the first light source.

  According to said structure, since the cold cathode fluorescent lamp whose luminous efficiency is good compared with another light source is used as a light source, there exists an effect that the brightness | luminance requested | required of an illuminating device is realizable with little power consumption.

(4) The second light source is a light emitting diode. The lighting device according to the present invention is characterized in that the second light source is a light emitting diode in order to solve the above-described problem.

  In this configuration, the lighting device according to the present invention uses a light-emitting diode as the second light source.

  According to the above configuration, the second light source is a light-emitting diode that can finely adjust the luminance as compared to the CCFL by increasing / decreasing the current or increasing / decreasing the LED duty and has a strong spectrum in a single color of R, G, or B. Therefore, the white balance can be finely controlled, and the color reproduction range of the combined light on the chromaticity coordinates can be expanded.

(5) Liquid crystal display device The liquid crystal display device according to the present invention includes the illumination device and a liquid crystal display panel that displays an image using illumination light from the illumination device in order to solve the above-described problems. It is characterized by.

  In this configuration, the electronic image formed on the liquid crystal display panel is presented to the user by the combined light of the lighting device.

  According to the above configuration, since the white balance of the illumination light quickly converges to the target value, the electronic image formed on the liquid crystal display panel converges to the target chromaticity immediately after the liquid crystal display device is activated. There exists an effect that it can show to a user using illumination light.

(6) Lighting Device Control Method On the other hand, the lighting device control method according to the present invention depends on the temperature in the lighting device and the driving amount of the first light source during the previous operation in order to solve the above-described problem. Then, the driving amount when the second light source is turned on is determined, and the first light source and the second light source are turned on.

  In this configuration, when the first light source and the second light source are turned on, when the drive is started with a fixed predetermined value as the drive amount of these light sources, the white balance immediately after the start of the drive is the target value. May be greatly rubbed. If the deviation is large, it is difficult to quickly converge the white balance of the combined light to the target value.

  Therefore, when the first light source and the second light source are turned on, the driving is not started with a fixed value as the driving amount of these light sources, but the temperature in the lighting device and the first time during the previous operation are not started. The driving amount when the second light source is turned on is adjusted according to the driving amount of the light source.

  By adjusting the driving amount at the time of lighting, the white balance of the combined light is made closer to the target value immediately after the start of lighting, and the convergence of the combined light to the target value of white balance is accelerated.

  According to the above configuration, since the white balance of the composite light can be made closer to the target value immediately after the start of lighting, the convergence of the white balance of the composite light to the target value can be accelerated. There is an effect that can be.

  (7) By the way, the lighting device may be realized by hardware, or may be realized by causing a computer to execute a program. Specifically, the program according to the present invention is a lighting device control program that causes a computer to operate as at least the control means described above, and the lighting device control program is recorded on the recording medium according to the present invention.

  When the lighting device control program is executed by a computer, the computer operates as the lighting device. Therefore, similar to the lighting device, the white balance of the composite light can be made closer to the target value immediately after the start of lighting, so that the white balance of the composite light can be converged to the target value. There is an effect that it can be accelerated.

  In addition, the illuminating device according to the present invention includes a temperature measuring unit (temperature sensor) that measures the temperature of the illuminating device in the illuminating device that emits different colors and includes the first light source and the second light source, and the previous time. A drive amount storage means (CCFL drive circuit) that stores the drive amount of the first light source during operation, controls the driving of the first light source and the second light source, and controls the measured temperature and the Control means (CCFL drive circuit, LED drive circuit, drive start LED duty determination processing unit, temperature CCFL duty table storage unit) for controlling the drive amount when the second light source is turned on in accordance with the stored drive amount The control means first determines a driving amount when the second light source is turned on when the lighting device is activated, and then turns on the first light source and the second light source. Characteristic It may be configured as follows.

  As described above, the lighting device according to the present invention determines the driving amount when the second light source is turned on according to the temperature in the lighting device and the driving amount of the first light source during the previous operation. And a control means for turning on the first light source and the second light source.

  Therefore, since the white balance of the composite light can be made closer to the target value immediately after the start of lighting, it is possible to accelerate the convergence of the white balance of the composite light to the target value. Play.

  On the other hand, the lighting device control method according to the present invention, as described above, when starting the lighting device, first, according to the temperature in the lighting device and the driving amount of the first light source at the previous operation, The driving amount of the second light source is determined, and then the first light source and the second light source are turned on.

  Therefore, since the white balance of the composite light can be made closer to the target value immediately after the start of lighting, it is possible to accelerate the convergence of the white balance of the composite light to the target value. Play.

  As an embodiment of the illumination device of the present invention, an embodiment used as a backlight of a liquid crystal television receiver will be described below. In the illumination device of the present embodiment, an example in which a 4-wavelength CCFL and an R-LED are combined has been described. However, the present invention is not limited to this, and the first light source has three or two wavelengths. CCFL may be used, and G-LED or B-LED may be used as the second light source.

  The CCFL of the present embodiment emits light containing a red component, and the wavelength peak of the red component is in the vicinity of 610 nm. Since CCFL does not emit light on the long wavelength side, it is used in comparison with the case where light emission of red component is shared only by R-LED by taking the form of assisting CCFL with R-LED having a peak around 640 nm. The number of R-LEDs to be reduced can be reduced, the cost can be reduced, and the reproducible color space can be expanded in the red direction.

  The liquid crystal television receiver according to the present embodiment will be described below with reference to FIGS.

  The main point in the description of the present embodiment is that when the hybrid backlight is activated, depending on the driving amount at the previous operation of the CCFL, that is, the CCFL duty (described later) and the temperature value of the hybrid backlight. By controlling the drive amount at the start of driving the R-LED, that is, LED duty (described later), the LED duty at the start of driving the R-LED is set to 0%, compared with the case of starting driving the R-LED. In other words, the convergence of the light white balance to the target chromaticity point is accelerated.

<About the block diagram of this embodiment>
FIG. 2 shows a block diagram of the liquid crystal television receiver in this embodiment and a functional block diagram in the LED control microcomputer.

  The main part of the liquid crystal television receiver is as follows: antenna 1, tuner 2, video signal processing circuit 3, LCD controller 4, liquid crystal panel 5, CCFL drive circuit 6, CCFL 7, LED control microcomputer 8, LED drive circuit 9, R- The LED 10 and the RGB sensor 11 are provided.

  The tuner 2 receives the television broadcast via the antenna 1, and sends the selected television broadcast content to the video signal processing circuit 3. The video signal processing circuit 3 converts the broadcast content video into a form that can be displayed on the liquid crystal panel, and sends it to the LCD controller 4. The LCD controller 4 sends the received broadcast content video to the liquid crystal panel 5 as a video signal. The liquid crystal panel 5 displays the video of the broadcast content as an electronic image based on the received video signal. The CCFL driving circuit 6 receives the clock signal from the LCD controller 4 and drives the CCFL 7 based on the clock signal.

  The CCFL drive circuit 6 includes a CCFL duty storage unit (not shown) that stores the changed CCFL duty when the CCFL duty, which is the driving amount for driving the CCFL 7, is changed. When the liquid crystal television receiver is activated, the CCFL driving circuit 6 starts driving the CCFL 7 using the CCFL duty at the previous operation stored in the CCFL duty storage unit.

  The LED control microcomputer 8 uses the RGB sensor 11 to measure the amount of combined light from the CCFL 7 and the R-LED 10. Based on the measurement result and the current LED duty from the LED drive circuit 9, the LED drive circuit 9 is instructed by the new LED duty so as to achieve an appropriate white balance. When starting up the liquid crystal television receiver, the LED control microcomputer 8 obtains the CCFL duty obtained from the CCFL drive circuit 6 during the previous operation of the CCFL 7 and the temperature in the lighting device obtained from the temperature sensor 12, that is, the CCFL 7 The LED duty when starting the driving of the R-LED 10 is obtained from the ambient temperature of the R-LED 10 and the LED duty is set in the LED driving circuit 9 as a new LED duty of the R-LED 10. The LED duty will be described later.

  The LED drive circuit 9 drives the R-LED 10 based on the new LED duty. When the LED duty of the R-LED 10 is changed and the luminance changes, the white balance changes. Therefore, again, the LED control microcomputer 8 uses the RGB sensor 11 to measure the current amount of combined light from the CCFL 7 and the R-LED 10. The loop from the light amount measurement by the RGB sensor 11 to the driving of the R-LED 10 is a loop, and the white balance of the combined light is repeatedly controlled.

<About CCFL duty (CCFL duty)>
In the liquid crystal television receiver in the present embodiment, the brightness adjustment of the CCFL is performed based on an instruction to adjust the screen brightness from the user.

  In the present embodiment, the brightness adjustment of the CCFL 7 is performed by changing the CCFL duty. The CCFL duty is expressed as a ratio of the time during which the drive current is supplied (turned on) to the CCFL in one cycle. For example, when one period is 50 μs and the time for turning on is 25 μs, the CCFL duty is 50%.

  The method of adjusting the brightness of the CCFL in the present invention is not limited to the method by changing the CCFL duty, and the brightness is adjusted by changing the current for driving the CCFL by controlling the current value using a constant current source circuit or the like. May be performed.

<LED duty (LED duty)>
In the present embodiment, the luminance adjustment of the R-LED 10 is performed by changing the LED duty. The LED duty is expressed as a ratio of a time during which a drive current is supplied (turned on) to the LED in one cycle. For example, when one period is 50 μs and the time for turning on is 25 μs, the LED duty is 50%.

  The method of adjusting the luminance of the LED in the present invention is not limited to the method by changing the LED duty, and the luminance is adjusted by changing the current for driving the LED by controlling the current value using a constant current source circuit or the like. May be performed.

<About the functional block diagram of this embodiment>
Next, the outline of each functional block in the LED control microcomputer 8 will be described. Details of the processing will be described later. The LED control microcomputer 8 executes a lighting device control program stored in a memory (not shown), and controls the above-described members, that is, the LED drive circuit 9 and the RGB sensor 11 as necessary. Thereby, the illuminating device of this embodiment can implement | achieve various functional blocks, and can operate said each member as an illuminating device.

First, the voltage chromaticity conversion processing unit 81 receives detection voltages corresponding to the light amounts of the R, G, and B colors detected by the RGB sensor 11. The voltage chromaticity conversion processing unit 81 obtains the brightness of the current combined light and the chromaticity coordinate value (x, y) of the XYZ color system from the received detection voltage using a predetermined calculation formula determined in advance. The obtained chromaticity coordinate value (x, y) is passed to the target chromaticity point x coordinate determination processing unit 82 and the LED duty correction amount determination processing unit 84. Target chromaticity point x-coordinate determination processing unit 82, the received chroma coordinates (x, y) on the basis of the y values of the black body radiation locus coordinates stored x ₀ is the x-coordinate value of the chromaticity point of the target The x coordinate value (x ₀ ) of the target chromaticity point acquired from the unit 83 is passed to the LED duty correction amount determination processing unit 84.

The LED duty correction amount determination processing unit 84 receives the current chromaticity coordinate value (x, y) of the combined light received from the voltage chromaticity conversion processing unit 81 and the target chromaticity point x coordinate determination processing unit 82. From the x coordinate value (x ₀ ) of the chromaticity point, a difference (Δx) between the x coordinate value (x) of the current chromaticity point and the x coordinate value (x ₀ ) of the target chromaticity point is obtained. Next, the LED duty correction amount determination processing unit 84 calculates an LED duty correction amount from the obtained difference (Δx) and the current LED duty acquired from the LED drive circuit 9. When determining the LED duty correction amount, the LED duty correction amount determination processing unit 84 refers to the LED duty correction amount table stored in the LED duty correction amount table storage unit 85 to determine the LED duty correction amount. Next, the LED duty correction amount determination processing unit 84 passes the determined LED duty correction amount to the LED duty addition processing unit 86. The LED duty addition processing unit 86 adds the current LED duty acquired from the LED drive circuit 9 and the LED duty correction amount received from the LED duty correction amount determination processing unit 84 to obtain a new LED duty, and the new LED duty Thus, the LED drive circuit 9 is operated.

  The above is the description of each functional block related to the white balance control loop. The functional blocks include functional blocks that operate only once when the liquid crystal television receiver is activated, in addition to functional blocks that repeatedly operate in these control loops. The description of these functional blocks is as follows.

  First, the drive start LED duty determination processing unit 87 acquires the CCFL duty at the previous operation of the CCFL 7 from the CCFL drive circuit 6 and acquires the current temperature from the temperature sensor 12.

  Next, the drive start LED duty determination processing unit 87 obtains the LED duty at the start of driving of the R-LED 10 from the acquired CCFL duty at the previous operation and the current temperature. When determining the LED duty, the drive start LED duty determination processing unit 87 refers to the temperature CCFL duty table stored in the temperature CCFL duty table storage unit 88 to determine the LED duty.

  Finally, the drive start LED duty determination processing unit 87 sets the determined LED duty as a new LED duty, and starts the operation of the LED drive circuit 9 with the new LED duty.

<About white balance control procedure>
1A and 1B show graphs for explaining a white balance control method according to the present embodiment. FIG.1 (b) is the figure which expanded the principal part of Fig.1 (a). FIG. 3 shows a flowchart of a procedure for controlling the white balance of the combined light of the hybrid backlight composed of the CCFL 7 and the R-LED 10.

  First, the control procedure will be described with reference to the flowchart of FIG. 3, and more specific description will be made with reference to FIGS. 1 (a) and (b).

  First, the drive start LED duty determination processing unit 87 acquires the CCFL duty at the previous operation of the CCFL 7 from the CCFL drive circuit 6 (S1a).

  Next, the drive start LED duty determination processing unit 87 measures the temperature in the hybrid backlight using the temperature sensor 12 (S1b).

  Next, the drive start LED duty determination processing unit 87 uses the CCFL duty at the previous operation and the measured temperature, and based on the temperature CCFL duty table shown in FIG. 6, the LED duty at the start of driving of the R-LED 10. And the LED duty is set in the LED drive circuit 9 (S1c).

  The temperature CCFL duty table shown in FIG. 6 is stored in the temperature CCFL duty table storage unit 88. What is the CCFL duty during the previous operation and what is the current temperature in the hybrid backlight? In addition, information on what percentage of LED duty should be used for driving the R-LED 10 is held as a table.

  For example, when the CCFL duty at the previous operation is 80% and the current temperature in the hybrid backlight is 16 degrees Celsius, the LED duty at the start of driving is 50%. In this temperature CCFL duty table, only representative values may be set, and values between them may be obtained by complementation.

  Next, the CCFL driving circuit 6 starts driving the CCFL 7 (S2). In the present embodiment, after the CCFL driving circuit 6 starts driving the CCFL 7, if the user gives an instruction to adjust the brightness of the screen of the liquid crystal television receiver, the brightness of the CCFL is based on the instruction. Make adjustments.

  Here, by turning on the CCFL 7 before the R-LED 10, as will be described later, the white balance feedback control is performed with a simple algorithm of “changing the LED duty of the R-LED 10 while measuring chromaticity”. Is possible.

  Next, the voltage chromaticity conversion processing unit 81 uses the RGB sensor 11 to measure a voltage value output according to the light amounts of R, G, and B colors of the hybrid backlight light (S3).

  Next, the voltage chromaticity conversion processing unit 81 calculates the current brightness of the hybrid backlight using a predetermined calculation formula (described later) from the measured voltage value (S4).

  Next, the voltage chromaticity conversion processing unit 81 determines whether or not the luminance calculated in S4 is equal to or higher than a predetermined set luminance (S5). When the calculated brightness is less than the predetermined set brightness, the process returns to S3 and the light quantity measurement process by the RGB sensor 11 is repeated again. If the calculated brightness is equal to or higher than the predetermined set brightness, the process proceeds to the conversion process from the detection voltage to chromaticity coordinates in S6.

  Here, when the calculated brightness is less than the predetermined set brightness, the process from S3 is repeated, and the reason why the process does not proceed to the next process after S6 is that the brightness of CCFL7 is not sufficient immediately after the start of driving. In this case, since the detection sensitivity of the RGB sensor 11 is low, there is a possibility that the next processing after S6 may not be performed properly, and when the R-LED 10 emits light with low luminance in accordance with CCFL7, there are a plurality of R This is because there is a possibility that the amount of light emission varies among individual LEDs.

  Next, the voltage chromaticity conversion processing unit 81 calculates the current chromaticity of the light of the hybrid backlight using a predetermined calculation formula (described later) from the measured voltage value (S6). The chromaticity is expressed using chromaticity coordinates (x, y) of the XYZ color system.

Next, the target chromaticity point x-coordinate determination processing unit 82 sets the target color to be a target of white balance control according to the chromaticity coordinate (x, y) of the current hybrid backlight light calculated in S6. The coordinates (x ₀ , y ₀ ) of the degree point are obtained (S7).

In the present embodiment, the deviation from the black body radiation locus is ± 0. 0 in order to obtain the coordinates (x ₀ , y ₀ ) of the target chromaticity point with respect to the chromaticity coordinates (x, y) of the current light. In the range of 02, coordinate data of a plurality of chromaticity points (x, y) is created as a table along the black body radiation locus, and stored in the black body radiation locus coordinate storage unit 83. Yes. The target chromaticity point x-coordinate determination processing unit 82 obtains a chromaticity point having a y-coordinate value (y ₀ ) closest to the y-coordinate value of the chromaticity coordinate (x, y) of the current light from the table, The chromaticity point is set as a target chromaticity point.

Next, the LED duty correction amount determination processing unit 84 determines the x-coordinate value (x) of the chromaticity point of the current light obtained in S6 and the x-coordinate value (x ₀ ) of the target chromaticity point obtained in S7. (Δx) is determined, and it is determined whether the absolute value of the difference (Δx) is smaller than a predetermined value (S8).

  If the absolute value of the difference (Δx) is smaller than the predetermined value, the current white balance has already sufficiently converged to the target value, so the LED duty is not corrected and the process returns to S3 and the next feedback control loop is executed. Start. If the absolute value of the difference (Δx) is greater than or equal to the predetermined value, the process proceeds to the LED light emission amount determination process in S9 in order to bring the current white balance closer to the target value.

  If it is determined in S8 that the absolute value of the difference (Δx) is equal to or greater than the predetermined value, the LED duty correction amount determination processing unit 84 calculates the difference (Δx) and the current LED duty acquired from the LED driving unit. Using the LED duty correction amount table shown in FIG. 4, the LED duty correction amount is determined (S9).

  The LED duty correction amount table shown in FIG. 4 is stored in the LED duty correction amount table storage unit 85. When the difference (Δx) is, and the current LED duty is, the LED duty is calculated. Information on what percentage should be corrected is held as a table. In this table, in order to prevent occurrence of hunting, the correction amount of the LED duty is set to be larger as the LED duty is higher, that is, as the luminance is higher and as the difference (Δx) is larger.

For example, when the difference (Δx) is minus 0.03 and the current LED duty is 70%, the correction amount of the LED duty is 10%. The difference is obtained by the equation Δx = _{x-x 0.} Since the current x-coordinate value is 0.03 smaller than the target x-coordinate value, the LED is increased so as to increase the brightness of the R-LED 10, that is, the current LED duty is added with a correction amount of 10%. The duty correction amount determination processing unit 84 issues an instruction to the LED duty addition processing unit 86.

  Next, the LED duty addition processing unit 86 adds the correction amount supported by the LED duty correction amount determination processing unit 84 to the current LED duty to obtain a new LED duty, and drives the R-LED 10 with the new LED duty. Thus, an instruction is issued to the LED drive circuit 9 (S10). Thereafter, the LED control microcomputer 8 returns the process to S3 and repeats the process in the feedback control loop.

  The above is the description of the procedure for controlling the white balance using the flowchart shown in FIG. In this description, the procedure for one loop in the feedback control loop has been described. Next, using the graph of FIG. 1, by controlling the feedback control loop twice, the chromaticity point of the white balance of the hybrid backlight is controlled so as to approach the target chromaticity on the chromaticity coordinates. Explain how.

FIG. 1A shows the relative positional relationship between the color reproduction range of the hybrid backlight light source, the black body radiation locus, and the chromaticity point of the single R-LED 10 when expressed in chromaticity coordinates. It is assumed that the chromaticity coordinates of the hybrid backlight light source at a certain time point are in the chromaticity coordinates (a ₀ ). In the present embodiment, only the luminance of the R-LED 10 is controlled to adjust the white balance. Therefore, the chromaticity of this light source connects the chromaticity coordinate (a ₀ ) point and the chromaticity point of the R-LED 10. However, it moves to the chromaticity coordinate point (a ₁ ) and the chromaticity coordinate point (a ₂ ) on the straight line indicated by the broken line. The control method will be described with reference to the enlarged view of the main part of FIG. 1A shown in FIG. 1B. The target chromaticity point only needs to be within a range of ± 0.02 from the black body radiation locus, but in the following description, it is assumed that the target chromaticity point is on the black body radiation locus for convenience.

First, by the process of S6, the voltage chromaticity conversion processing unit 81 obtains the current chromaticity of the light source. It is assumed that the current chromaticity is at the chromaticity point (a ₀ ).

Next, in step S7, the target chromaticity point x coordinate determination processing unit 82 obtains a target chromaticity point (w ₀ ) corresponding to the chromaticity point (a ₀ ) of the current light source. The target chromaticity point (w ₀ ) is a point on the black body radiation locus having the y coordinate value closest to the y coordinate value of the chromaticity point (a ₀ ).

Next, the determination process of S8, LED duty correction amount determination processing unit 84, x-coordinate value of the x coordinate value of the chromaticity point _{(a 0)} (x) and the target chromaticity point _{(w 0) (x 0)} It is determined that the difference (Δx) is greater than a predetermined value.

  Next, the LED duty correction amount determination processing unit 84 and the LED duty addition processing unit 86 correct the LED duty of the R-LED 10 by the processes of S9 and S10.

Next, the voltage chromaticity conversion processing unit 81 obtains the current chromaticity of the light source by the processing of S6. The current chromaticity is the chromaticity point (a ₁ ). By correcting the LED duty, the chromaticity of the current light source is the chromaticity point (a ₀ ) on the chromaticity coordinates and the chromaticity of the R-LED 10 alone. This is because the chromaticity point (a ₀ ) moves to the chromaticity point (a ₁ ) on the straight line connecting the points. In this example, since the R-LED 10 moves in the direction of increasing the luminance, the R in the synthesized light increases at the chromaticity point (a ₁ ).

Next, by the processing of S7, the target chromaticity point x coordinate determination processing unit 82 obtains the target chromaticity point (w ₁ ) corresponding to the chromaticity point (a ₁ ) of the current light source. The target chromaticity point (w ₁ ) is a point on the black body radiation locus having the y coordinate value closest to the y coordinate value of the chromaticity point (a ₁ ).

Next, the determination process of S8, LED duty correction amount determination processing unit 84, x-coordinate value of the chromaticity point _{(a 1)} (x) and the target chromaticity point x-coordinate value of _{(w 1) (x 1)} It is determined that the difference (Δx) is greater than a predetermined value.

  Next, the LED duty correction amount determination processing unit 84 and the LED duty addition processing unit 86 correct the LED duty of the R-LED 10 by the processes of S9 and S10.

Next, the voltage chromaticity conversion processing unit 81 obtains the current chromaticity of the light source by the processing of S6. The current chromaticity is the chromaticity point (a ₂ ).

Next, by the processing of S7, the target chromaticity point x coordinate determination processing unit 82 obtains the target chromaticity point (w ₂ ) corresponding to the chromaticity point (a ₂ ) of the current light source.

Next, the determination process of S8, LED duty correction amount determination processing unit 84, x-coordinate value of the x coordinate value of the chromaticity point _{(a 2)} (x) and the target chromaticity point _{(w 2) (x 2)} It is determined that the difference (Δx) is smaller than a predetermined value.

  As described above, the current chromaticity point returns to the black body radiation locus so that the current chromaticity point is on the black body radiation locus, and even if the current chromaticity point deviates from the black body radiation locus for some reason. So that the feedback control loop is always working.

  In this feedback control loop, one loop must be fast. This is because the target chromaticity point is converged earlier. Specifically, the time required for one loop is preferably about 5 ms, for example, and is preferably at a speed that allows feedback control to be performed three times within a period (16 ms) for displaying one frame of an image.

  Further, if the illumination light is composed only of the wavelength component of CCFL 7 at the start of the lighting device, there arises a problem that the chromaticity of the illumination light becomes blue-green (cyan). At this time, since the white balance is likely to be disturbed after the CCFL 7 is turned on and still less than the predetermined luminance, the liquid crystal display panel is set in a completely light-shielded state so that the illumination light of the illumination device is not output. . Thereby, even if the white balance is disturbed after the CCFL 7 is turned on, the light in the state where the white balance is disturbed does not reach the user, so that the user watching the liquid crystal display device does not feel uncomfortable.

<Calculation formula for obtaining luminance and chromaticity coordinates from detection voltage>
In order to obtain the luminance and chromaticity coordinates from the value of the current amount of synthesized light detected as a voltage by the RGB sensor 11, the following three procedures are performed. Procedures 1 and 2 are procedures performed before shipment of the television receiver of the present embodiment, and procedure 3 is performed when the television receiver is used or during actual white balance control. In this processing, the voltage chromaticity conversion processing unit 81 performs.

(Procedure 1)
First, monochromatic R, G, and B tristimulus values (X _R , Y _R , Z _R ,..., Z _B ) are measured, and a matrix of Equation 1 and an inverse matrix of Equation 2 are created.

  The matrix and the inverse matrix are stored in the LED control microcomputer 8 as data common to each television receiver to be shipped.

(Procedure 2)
Conversion coefficients (a, b, c) are used to convert voltage values, which are detection amounts by the RGB sensor 11, into RGB tristimulus values. In order to obtain this conversion coefficient, as initial values, for example, a detection amount (V _R0 , V _G0 , V _B0 ) for a certain color (F ₀ ) such as white, and an XYZ tristimulus value (X _0). , Y ₀ , Z ₀ ), the matrix of Equation 1, and the inverse matrix of Equation 2. RGB tristimulus values (R ₀ , G ₀ , B ₀ ) of a certain color (F ₀ )

Can be written.

  Further, the conversion from the RGB color system to the XYZ color system can be performed by assuming that the tristimulus values in the RGB color system and the XYZ color system are (R, G, B) and (X, Y, Z), respectively. Using the matrix of Equation 1,

Therefore, from Equation 3 and Equation 4,

Thus, the transformation coefficient (a, b, c) is obtained by solving the equation (6).

(Procedure 3)
In order to convert the detection amount of the RGB sensor 11 into luminance and chromaticity, when the detection amount of the RGB sensor 11 with respect to a certain color (F) to be converted is (VR, VG, VB), the conversion coefficient obtained by Expression 6 And from Equation 4, the tristimulus values (X, Y, Z) of the XYZ color system are

Can be written. Here, Y represents luminance.

  Conversion from tristimulus values (X, Y, Z) to chromaticity (x, y) is performed by the following equation.

  By calculating Equation 7 and Equation 8, the detection amount by the RGB sensor 11 is converted into luminance Y and chromaticity (x, y).

<Reasons for controlling the white balance on the black body radiation locus>
As described in the problem of the prior art, it is impossible to always converge the white balance of the light source of the hybrid backlight composed of the CCFL 7 and the R-LED 10 to one point on the chromaticity coordinates.

  Therefore, in the present invention, in controlling the white balance of the combined light of the light source of the hybrid backlight, instead of controlling a certain point on the chromaticity coordinates as a target point, the color does not change, that is, The basic idea is to converge to any of coordinate points that can be easily converged by simple control among a plurality of arbitrary coordinate points having the same color.

  In the present embodiment, a range with a deviation of ± 0.02 from the black body radiation locus is adopted as the range for taking the plurality of arbitrary coordinate points. Further, it is not necessary to use the entire color temperature range as the black body radiation locus. For example, a black body radiation locus in a region where the hue is white or almost white, such as 3000K to 30000K, may be used. A black body radiation locus having a lower color temperature may be used as long as an area having a yellow-red hue is also included. If a blue region whose hue is close to white is also included, a black body radiation locus having a higher color temperature may be used.

  In FIG. 5, on the chromaticity coordinates of the XYZ color system, the color reproduction range, the black body radiation locus, and the deviation from the black body radiation locus of the hybrid backlight according to this embodiment are within ± 0.02. The graph which plotted is shown. The black body radiation locus shows only a part.

  The reason for using the black body radiation locus is that the black body radiation locus is in the whitest range on the chromaticity coordinates, and if the white balance converges on the black body radiation locus, different coordinates on the black body radiation locus This is because the color of the synthesized light does not change even if it is a point. The reason why the deviation is in the range of ± 0.02 is that, even if the target point is not completely on the blackbody radiation locus, there is no practical problem and control is facilitated within this range. is there.

Here, what should be noted when setting the arbitrary coordinate point is, for example, in the case of this embodiment, the y coordinate value of the target chromaticity point equal to or more than the y coordinate value (y) of the current chromaticity point. (y ₀₎ most sought approximate y coordinate values of the target chromaticity points (y ₀₎ of, and is the y-coordinate value of the target chromaticity point (y ₀₎ and the set, the target chromaticity point x Since the coordinate value (x ₀ ) is obtained, the arbitrary coordinate point needs to be set so that the current chromaticity point and the target chromaticity point have a one-to-one correspondence. For example, for the current chromaticity point (x, y), a plurality of corresponding target chromaticity points, that is, target chromaticity point 1 (x ₀ , y ₀ ) and target chromaticity point 2 (x ₁ , y ₀ ) as there is no (value different from x ₀ and x _1), sets an arbitrary coordinate point.

In this embodiment, the target chromaticity point is obtained using the y coordinate value (y) of the current chromaticity point. However, the present invention is not limited to this configuration, and the current chromaticity point x coordinates x-coordinate value of equal to or more certain target chromaticity point with (x) (x ₀₎ x-coordinate value of the target chromaticity point most similar among the search of (x _0), the target chromaticity point A configuration in which the y coordinate value (y ₀ ) of the target chromaticity point paired with the x coordinate value (x ₀ ) may be obtained.

  Further, the line on the chromaticity coordinates for converging the white balance is preferably a black body radiation locus, but is not limited thereto. That is, the current chromaticity point and the target chromaticity point have a one-to-one correspondence and may be a set of arbitrary lines or arbitrary coordinate points as long as the color does not change.

<About another configuration for obtaining target chromaticity points>
In the present embodiment, the target chromaticity point with respect to the chromaticity of the current combined light obtained from the light amounts of the R, G, and B colors measured by the RGB sensor 11, that is, the black body radiation locus and the deviation from it are ± 0. .02, a combination of coordinate values (x, y) representing the arbitrary chromaticity points held in the black body radiation locus coordinate storage unit 83 when determining the chromaticity coordinates of the arbitrary chromaticity points in the range of .02 The table is used. However, the present invention is not limited to this configuration. The target chromaticity point x-coordinate determination processing unit 82 performs calculation for obtaining the target chromaticity point using an approximate expression representing an arbitrary line such as a black body locus, for example, and the LED control microcomputer 8 sets the white balance to the arbitrary value. The brightness of the LED may be adjusted to converge on the line.

<About another configuration for obtaining the driving amount of the LED light source>
In the present embodiment, when the drive amount of the R-LED 10 is obtained, the temperature in the illumination device held in the temperature CCFL duty table storage unit 88, the drive amount of the CCFL 7 at the previous operation, and the drive amount of the R-LED 10 A combination table is used. However, the present invention is not limited to this configuration. You may use the approximate expression which calculates | requires the drive amount of R-LED10 by the temperature in an illuminating device, and the drive amount of CCFL7 at the time of last operation | movement.

<About the light source>
In the present embodiment, a white light emitting backlight device is configured by using a white light emitting CCFL (cold cathode fluorescent lamp) as a first light source and a red light emitting LED (light emitting diode) as a second light source. Although described, the present invention is not limited to this. For example, a red light emitting LED is used as the first light source, and a blue light emitting LED or a green light emitting LED is used as the second light source. It is obvious that various light sources that emit colors may be used as appropriate.

<Supplementary items>
The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  Finally, each block of the liquid crystal television receiver, particularly the LED control microcomputer 8, may be configured by hardware logic, or may be realized by software using a CPU as follows.

  That is, the liquid crystal display device includes a CPU (central processing unit) that executes instructions of a control program for realizing each function, a ROM (read only memory) that stores the program, a RAM (random access memory) that expands the program, A storage device (recording medium) such as a memory for storing the program and various data is provided. An object of the present invention is to provide a recording medium in which a program code (execution format program, intermediate code program, source program) of a control program of the LED control microcomputer 8 which is software for realizing the functions described above is recorded so as to be readable by a computer. This can also be achieved by supplying the liquid crystal display device and the computer (or CPU or MPU) reading and executing the program code recorded on the recording medium.

  Examples of the recording medium include a tape system such as a magnetic tape and a cassette tape, a magnetic disk such as a floppy (registered trademark) disk / hard disk, and an optical disk such as a CD-ROM / MO / MD / DVD / CD-R. Card system such as IC card, IC card (including memory card) / optical card, or semiconductor memory system such as mask ROM / EPROM / EEPROM / flash ROM.

  The liquid crystal display device may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, satellite communication. A net or the like is available. Also, the transmission medium constituting the communication network is not particularly limited. For example, even in the case of wired such as IEEE 1394, USB, power line carrier, cable TV line, telephone line, ADSL line, etc., infrared rays such as IrDA and remote control, Bluetooth ( (Registered trademark), 802.11 wireless, HDR, mobile phone network, satellite line, terrestrial digital network, and the like can also be used. The present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

  According to the present invention, an illuminating device that can control white balance can be realized with simple control. Therefore, the illuminating device can be widely used for various systems including a liquid crystal television receiver, a cellular phone, and a portable electronic device incorporating the illuminating device. Can be used for

6 is a graph showing how white balance is controlled to converge on a black body radiation locus in the embodiment of the present invention, and (a) shows the overall positional relationship on the chromaticity coordinates of the XYZ color system. It is a graph to show, (b) is the enlarged view which expanded the principal part. It is a block diagram and a functional block diagram of the principal part of a liquid crystal television receiver in an embodiment of the present invention. 5 is a flowchart illustrating a procedure for controlling white balance in the embodiment of the present invention. In the embodiment of the present invention, this is a table used when the correction amount of LED duty is obtained from the difference (Δx) between the current chromaticity and the target chromaticity and the current LED duty. In the embodiment of the present invention, the color reproduction range of the light source of the lighting device, the locus of the portion used for white balance control in the black body radiation locus, and the range where the deviation from the black body radiation locus is within ± 0.02. It is the graph which showed the line to show on the chromaticity coordinate of an XYZ color system. In the embodiment of the present invention, this is a table used to determine the LED duty at the start of driving the R-LED from the CCFL duty at the previous operation of the CCFL and the current temperature of the hybrid backlight. . It is the graph which showed the mode of the conventional white balance control in the case of CCFL of the manufacture initial stage, and the case of CCFL after progress of 100,000 hours on the chromaticity coordinate of XYZ color system.

Explanation of symbols

1 Antenna 2 Tuner 3 Video Signal Processing Circuit 4 LCD Controller 5 Liquid Crystal Panel 6 CCFL Drive Circuit 7 CCFL
8 LED control microcomputer 9 LED drive circuit 10 R-LED
11 RGB sensor 12 Temperature sensor 81 Voltage chromaticity conversion processing unit 82 Target chromaticity point x coordinate determination processing unit 83 Black body radiation locus coordinate storage unit 84 LED duty correction amount determination processing unit 85 LED duty correction amount table storage unit 86 LED duty Addition processing unit 87 Driving start LED duty determination processing unit 88 Temperature CCFL duty table storage unit

Claims (8)

In a lighting device having a first light source and a second light source that emit different colors,
The driving amount when the second light source is turned on is determined according to the temperature in the lighting device and the driving amount of the first light source during the previous operation, and the first light source and the second light source are turned on. An illumination device comprising a control means. The control means, when determining the driving amount when the second light source is turned on,
The temperature in the lighting device,
The driving amount of the first light source during the previous operation;
The lighting device according to claim 1, wherein a table including a driving amount when the second light source is turned on is used.   The lighting device according to claim 1, wherein the first light source is a cold cathode fluorescent lamp.   The lighting device according to any one of claims 1 to 3, wherein the second light source is a light emitting diode. The lighting device according to any one of claims 1 to 4,
A liquid crystal display device comprising: a liquid crystal display panel that displays an image using illumination light from the illumination device. In a method of controlling an illumination device that emits different colors and has a first light source and a second light source,
The driving amount when the second light source is turned on is determined according to the temperature in the lighting device and the driving amount of the first light source during the previous operation, and the first light source and the second light source are turned on. A control method of a lighting device characterized by the above.   An illumination device control program for causing a computer to function as the illumination device control means according to any one of claims 1 to 5.   The computer-readable recording medium which recorded the illuminating device control program of Claim 7.

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